1. Field of the Invention
The present invention relates to methods for manufacturing laminated ceramic electronic components, such as laminated capacitors, and more particularly, the present invention relates to a method including an improved step of forming external electrodes for manufacturing a laminated ceramic electronic component.
2. Description of the Related Art
Conventionally, laminated ceramic electronic components, such as laminated inductors, are manufactured by a method described below. First, a ceramic green sheet is formed on a carrier film, such as a polyethylene terephthalate film. Subsequently, on the ceramic green sheet, an internal electrode is printed by screen printing or other process. Next, after the ceramic green sheet formed on the carrier film is laminated on a lamination stage or on a ceramic green sheet previously laminated thereon and is then bonded by compressing, the carrier sheet is then removed. The steps described above are repeatedly performed. Alternatively, ceramic green sheets separated from the corresponding carrier films are laminated with each other and are then bonded by compressing. As described above, a mother laminate is produced.
Subsequently, the mother laminate is cut into individual laminates each forming one laminated ceramic element. The individual laminate thus formed defining one laminated ceramic electronic component is fired, thereby yielding a sintered body. The sintered bodies are processed by barrel polishing to form round corner portions and are then aligned by using an aligning tool.
Next, a conductive paste is applied to edge surfaces of the sintered body for forming external electrodes and is then dried. The sintered bodies provided with the conductive paste are aligned in an oven, and the conductive paste is then fired, whereby the external electrodes are formed on the individual sintered bodies. In addition, when necessary, a plating film is formed on the surface of the external electrode by firing the conductive paste.
In a conventional manufacturing method for a laminated ceramic electronic component, in order to form an external electrode, a process that must be performed includes the steps of aligning and holding sintered bodies by using an aligning tool, applying a conductive paste thereon, drying the conductive paste, removing the sintered bodies from the tool, placing the sintered bodies provided with the conductive paste in an oven, and firing the conductive paste. That is, a number of steps must be performed for forming the external electrodes, and hence, the method described above has problems in that the manufacturing process is complicated and the manufacturing cost is high.
In addition, since the internal electrode and the external electrode are formed in different steps, the reliability of electrical connection between the internal electrode and the external electrode may be degraded in some cases due to (1) the shrinkage of a portion of the internal electrode which is exposed on the external surface of the sintered ceramic body, (2) the precipitation of a glass frit in the conductive paste constituting the internal electrode, and (3) the generation of bubbles due to air trapped during application of the conductive paste.
In order to overcome the problems described above, preferred embodiments of the present invention provide a method for manufacturing a laminated ceramic electronic component which allows for easy formation of external electrodes, and in addition, significantly improves the reliability of electrical connection between the internal electrode and the external electrode. In addition, preferred embodiments of the present invention provide a laminated ceramic electronic component manufactured by the method described above.
In accordance with a preferred embodiment of the present invention, a method for manufacturing a laminated ceramic electronic component includes the steps of forming composite sheets each having a conductor and a ceramic layer provided at the side of the conductor on a carrier film, laminating the composite sheets with each other to obtain a first laminated body, cutting the first laminated body in the thickness direction thereof so as to divide the conductor to obtain a second laminated body having the conductor exposed on the cut surface, and firing the second laminated body to obtain a sintered ceramic body having an external electrode formed of the exposed conductor.
In the method for manufacturing the laminated ceramic electronic component according to this preferred embodiment, the laminating step preferably includes the steps of press-bonding the composite sheet formed on the carrier sheet to a lamination stage or to a composite sheet that was previously laminated, separating the carrier film from the composite sheet, and repeating the steps of press bonding and separating.
In the method for manufacturing the laminated ceramic electronic component according to this preferred embodiment, the laminating step also preferably includes the steps of separating the composite sheets from the carrier films, laminating the composite sheets with each other after separating, and compressing the laminated body in the thickness direction thereof.
In the method for manufacturing the laminated ceramic electronic component described above, the forming step preferably includes a step of printing the conductor and the ceramic layer at least two times so as to form a composite sheet including a plurality of conductor layers and a plurality of ceramic layers.
In the method for manufacturing the laminated ceramic electronic component described above, a planar configuration of the external electrode preferably includes an edge surface portion extending along the cut surface exposed by the cutting and a pair of bent portions bent inside from the cut surface at the both ends of the edge surface portion.
In the method for manufacturing the laminated ceramic electronic component described above, the cutting step preferably includes a step of cutting the first laminated body in a direction that is substantially perpendicular to the cut surface for forming a second laminated body having a substantially rectangular shape having a pair of edge surfaces and a pair of side surfaces connecting therewith, wherein the pair of bent portions are arranged to extend to the pair of side surfaces.
In the method for manufacturing the laminated ceramic electronic component described above, the conductor of a composite sheet disposed at the outermost layer of the first laminated body preferably has a bent portion extending inside from the edge surface portion of the external electrode which is exposed by the cutting.
In the method for manufacturing the laminated ceramic electronic component described above, the external electrode having the edge surface portion and the pair of bent portions is arranged such that the inner portion of the corner defined by the edge surface portion and the bent portion has a substantially round configuration.
In the method for manufacturing the laminated ceramic electronic component described above, the external electrode having the edge surface portion and the pair of bent portions is formed such that the outer portion of the corner defined by the edge surface portion and the bent portion has a substantially round configuration.
In the method for manufacturing the laminated ceramic electronic component described above, a width of the edge surface portion of the external electrode including the edge surface portion and the pair of bent portions increases toward an outer surface of the laminated body along the laminating direction.
In the method for manufacturing the laminated ceramic electronic component described above, widths of the pair of bent portions of the external electrode including the edge surface portion and the pair of bent portions increase toward an outer surface of the laminated body along the laminating direction.
In the method for manufacturing the laminated ceramic electronic component described above, the forming step preferably includes a step of forming a second conductor constituting an internal electrode at the same time when the conductor is formed.
In accordance with another preferred embodiment of the present invention, a laminated ceramic electronic component includes a sintered ceramic body formed by an integral firing technique for a laminated ceramic, and a plurality of external electrodes arranged so as to be exposed on the outer surface of the sintered ceramic body, wherein the outer surface of the external electrode is flush with the outer surface of the sintered ceramic body.
Other features, elements, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments thereof with reference to the attached drawings.